Objects are not exported
I took a look at your file. 
You can see your objects in wireframe only because there are no faces in the object's data, they are only vertices and edges.

Quick solution to solve it would be to 


select the object
TAB into edit mode
be in vertex select mode or edge select mode
select everything and fill with "F"

This works in most of the cases, sometimes you remain with some unfilled faces that you have to fill manually selecting usually two opposite edges and fill with "F". 


I have tried this with a few objects and exported as .obj, opened it with a cad software and the filled objects are exported.